Warm milk is good.
I have a tip if you want to sleep.
Put a bath on to run, go on a ten minute run (roughly twice round your block), come back, turn your bath off. Warm yourself up some milk (this takes two seconds - put a tiny amount of water in the bottem so that you dont end up with spunky resiues to clean off) - you can put vanilla essence or anything which wont give you energy (i.e. sugar).
Go and relax in the HOT bath for half an hour and drink your warm milk. Make sure your bath is as hot as you can bear it. Dont get out until you feel lethargic.
Get out and sleep IMMEDIATELY.
I find it helps to have the radio on. Something like Radio 5 is good as they talk about current affairs irreverantly.
Do NOT eat a mssive meal in the evening.